This invention relates to a method for molding multi-part assemblies and to products formed by such methods. More particularly, it concerns a method for molding support assemblies for spread rollers of photographic cameras and similar apparatus in which one of two rollers is journalled at each end in a support plate while the other of the two rollers is journalled at each end in a movable, spring-loaded bearing block slidable in the support plate. The method involves a two-shot molding technique by which the slidable bearing block is molded in place using the sliding guide surfaces of the support plate as a partial mold cavity.
In a commonly assigned U.S. Pat. No. 4,253,757 issued Mar. 3, 1981 to Harvey S. Friedman and Leon Rubinstein, there is disclosed a spread roller assembly which is of a general class of such assemblies to the extent that it includes a pair of juxtaposed rollers adapted to be incorporated in the access door housing of a photographic camera and operative for spreading a processing fluid across a layer on an exposed film unit to initiate the formation of a visible photographic image in the film unit. In the patent disclosure, opposite ends of one of the two rollers, specifically the top roller, are journalled directly in a plate-like support member of molded plastic material. The molded support member is shaped to facilitate connection directly to the access door housing by snap fit, to provide a pivotal mounting of the access door housing from the camera body and to support various related components such as a door latch and the like. The bottom roller is journalled at each end in a movable bearing block also formed of molded plastic material and adapted to be assembled with and slidably received in the support member for relative vertical movement. The movable bearing blocks are each biased upwardly by a coil spring acting between it and the support member. The movable bearing block is further configured to define a forwardly curved film engaging formation which though moved out of physical engagement with the film unit passing through the rollers as a result of downward displacement of the bottom roller by the thickness of the film unit, moves upwardly to engage the film unit as the trailing end thereof exits from the nip of the two rollers.
The spread roller support arrangement disclosed in the aforementioned patent has been demonstrated to be advantageous not only from the standpoint of providing improved spread roller performance in processing film units exposed in instant cameras as compared with prior arrangements, but more significantly from the standpoint of greatly reduced material and manufacturing costs. In this latter respect, the formation of the plate-like support members and movable bearing blocks from molded plastics and the facility provided for the use of simple low-cost coil springs to develop the needed nip pressure between the rollers result in important cost savings by comparison to prior extensive use of stamped metal for both the roller supports and in specially fabricated leaf springs. Nevertheless, the requirement for assembly of individually formed parts remains as an increment of manufacturing cost of substantial magnitude in light of the large numbers of spread roller assemblies used in the instant camera art. Accordingly, there is need for improvement in spread roller assemblies of the type disclosed in the aforementioned patent, particularly in reducing the time required for the assembly of each unit.